The invention relates generally to a field emission device using carbon nanotubes. More particularly, the present invention relates to a vacuum field emission device using carbon nanotubes grown in a direction parallel to a substrate.
Emission of electrons in the field emission device is greatly varied depending on the structure of a device, the materials constituting a cathode and the shape of the cathode. Presently, the structure of the field emission device may be classified into a diode type consisted of a cathode and an anode, and a triode type consisted of a cathode, a gate and an anode. The triode type structure can be driven with low voltage compared to the diode type since it applies an electric field to the cathode and its neighboring gate in order to emit electrons. Further, the triode type can control easily the current applied into its gate as well as anode. However, there is a problem that the manufacturing of the triode type is not easy due to its complicated structure.
The materials constituting the cathode include a metal, silicon, diamond, diamond like carbon, carbon nanotube, etc. If the carbon nanotube is used as the cathode materials, a good field emission device could be obtained due to a high field emission characteristic and a high chemical and mechanical stability of the carbon nanotubes. If a field emission device is manufactured using the carbon nanotubes as the cathode, it can be easily applied to a microwave vacuum device, a flat display device, etc.
The field emission device using the carbon nanotube emitter, which has been attempted so far, employs a field emission emitter. The field emission emitter is manufactured by a process in which carbon nanotube is grown using arc discharge or laser vaporization method and then coated it on a substrate using a thick film process, or a process in which after depositing catalyst metal on a main board, the carbon nanotubes are grown in a vertical direction to the main board. In case of the latter, it is possible to manufacture the device using a semiconductor process. However, as the carbon nanotubes grown randomly are irregular in length, it is difficult to make uniform device. Also, there exists a problem in a vacuum packaging peculiar to the conventional field emission display. Further, there is a problem in the adhesion stability of the tube since the structure of the device becomes three-dimensional. In addition, there is a problem that application to subsequent semiconductor processes is made difficult due to existence of a space between the tubes.
The present invention provides a method of manufacturing a field emission display using an edge emitting for improving subsequent semiconductor processes, in a way that a metal catalyst is selectively deposited at the side walls of the pattern so that carbon nanotubes can be grown in a direction parallel to the catalyst metal and the grown carbon nanotubes are attached on a basic material by a coating process.
According to the present invention, a field emission device using carbon nanotubes is disclosed, including a non-conductive substrate 110 acting as a basic material, a cathode electrode 151 formed on the non-conductive substrate 110, a transparent upper plate 180 and an anode electrode is characterized in that it comprises an insulating layer 140 stacked on a portion of the cathode electrode 151, for electrically isolating the cathode electrode 151 from the anode electrode, the portion neighboring to the anode electrode on the an upper portion of the cathode electrode 151; a conductive metal catalyst 120 coated at least at a portion of sidewall opposite to the anode electrode on the sidewall of the insulating layer 140; and a carbon nanotube emitter 130 grown in the direction parallel to the non-conducting substrate 110 from the surface of the metal catalyst 120, wherein the metal catalyst 120 electrically connects the carbon nanotube emitter 130 and the cathode electrode 151.
Also, a method of manufacturing a field emission device using carbon nanotubes is disclosed that includes the steps of forming a cathode electrode 151 on a non-conductive substrate 110 acting as a basic material through patterning; forming an insulating layer 140 for an electrical isolation on the cathode electrode 151 while exposing a portion of the cathode electrode 151; selectively coating a metal catalyst 120 on the exposed portion of the cathode electrode 151 at one side wall of the insulating layer 140; growing at least one carbon nanotube emitter 130 adhered to the metal catalyst 120 and in a direction parallel to the non-conductive substrate 110; and forming a fluorescent thin film 160 at a point spaced by a given distance with the carbon nanotube emitter 130 on the non-conductive substrate 110.